1. Field of the Invention
This invention relates to a method and an apparatus for achieving chemical-mechanical jet etching of features in a workpiece such as a semiconductor substrate or a built-up stack of films. In particular, the invention permits high etch rates for thinning the workpiece or for production of relatively large dimension etched features in such a workpiece, such as trenches and through-wafer vias for electrical contacts, or reservoirs for ink-jet heads, where critical dimensions are relatively large, on the order of 1–100 microns, or for thinning in the range of 100–1000 microns.
2. Brief Description of the Background Art
Various wet-chemical etching, dry-etching (i.e., various forms of plasma etching) and electrochemical methods exist which permit creation of features on a semiconductor substrate or on a stack of layers of semiconductor, conductor, and dielectric materials, or similar flat structure, generally using various sorts of patterned masks to control where underlying material is etched away and where it is left in place. Such methods provide the required degree of precision for etching semiconductor features with critical dimensions in the submicron range, but typically achieve etch rates in the range of about 1 micron or less of thickness per minute. Where the required features are relatively large-scale, in the range of from about 10 to about 100 microns, as in making a through-wafer via or large trench on a silicon wafer, or the amount of material to be removed is large, as in wafer thinning applications, and the required precision is less critical, the etch rates achievable by such methods are generally too low to be practical in commercial production. What is needed is a method permitting the removal of large amounts of silicon wafer or other material, with moderate precision, at etch rates sufficiently rapid to be practical in industrial semiconductor processing.